The present invention relates generally to data storage systems. More specifically, the present invention relates to a method and system for the management of data in high-density data storage systems.
Data storage systems comprise storage devices such as hard-disk drives, floppy drives, tape drives, compact disks, etc. Conventionally, tape-based storage systems are used for storing large volumes of data including making “backups” of data for recovery purposes in case of a loss of the backed-up data. Though tape drives are an inexpensive way of backing up large amounts of data, they can be slow in speed. Further, tape-based storage systems do not offer sufficient protection against data corruption, user error and device failures while data are being written to or read from the tape. Even state-of-the-art tape-based storage technologies, such as the Linear Tape Open (LTO) and Super Digital Linear Tape (SDLT), are substantially slower than disk-based storage systems, such as a Redundant Array of Inexpensive/Independent Disks (RAID). RAID systems employ a combination of multiple disk drives for data storage, and allow redundancy of stored data, which ensures data integrity in the case of a disk failure. Recovery from a disk failure can also be automated within RAID systems, by using data redundancy and parity generation.
Replacing tape-based storage systems with disk-based storage systems can increase speed, improve reliability, and eliminate delays in loading and searching for a tape for the required data. However, this replacement requires new software and exhaustive redesigning of present computing systems and applications. In order to avoid this problem, virtual tape libraries (VTL) are used.
A VTL is a configuration or design that makes an array of disk drives, such as a RAID array, seem like a tape library to a computing system or application. This can be achieved with the minimum addition of new software to the computing system or minimum redesigning of the computing system. The tape library includes multiple tape drives. VTLs are fast and can be shared among multiple computing systems, such as multiple media servers, running different applications. Data may also be allocated disk space in a static or dynamic way in VTLs.
However, as the number of disk drives in RAID systems increase, power consumption becomes high since, to maintain fast random-access of a disk, each disk drive that might be needed has to be powered on in a constant and fast spinning state. Therefore, disk-based storage systems consume more power than tape-based ones with equal storage capacity. In addition, as the number of powered drives increases, the probability of the failure of a disk drive also goes up.